This application is a 371 of PCT/NL99/00170, filed on Mar. 25, 1999.
The present invention relates to a device for treating a fluid.
Such a device is known from the French patent specification 1,506,445. This specification discloses a device wherein a common drive is provided for both the rotation of the rotational member and the indexing movement of the auxiliary members. This drive comprises an electromagnet and a spring. The rotational movement is realized by the continuous pressure force of the spring. With a detent mechanism the rotating member is connected with the driving move of the spring. The spring is compressed by retracting the electromagnet by energization. During this retracting movement the auxiliary member also moves back but because of the detent mechanism desribed above this is not true for the rotating member. This device is a laboratory device, i.e. analytically for very small quantities of material. During the return movement by the electromagnetic force the rotating member will move slower and probably even stop. The return movement is a very fast uncontrolled movement.
It is not possible to upscale such a structure. Upscaling means industrial application of chromatography columns. Columns are used having a size of e.g. a meter and a diameter of some centimeters up to a meter or more. The rotating member, the support frame respectively on which such columns are provided, can have a weight of many hundreds of kilos to hundreds of tons. The indexing movement according to the French patent specification 1,506,445 is not possible therein. During the fast return movement, as is realized with the electomagnetic force, unacceptable damage will occur at the separation face between the rotating member and the auxiliary member.
The subject inventions aims to provide a device which can be used on industrial xe2x80x98largexe2x80x99 scale and wherein the to-and fro movement of the auxiliary member as described above is possible.
This aim is realised with a device as described above having the characteristic features of claim 1. It is suggested to use sensors and have these sensors to effect the movement of the auxiliary member, the rotating member respectively because in an industrial apparatus, the movement of the rotating member with regard to the auxiliary member is difficult to control. In this way it is possible to realize the openings of the auxilliary member and rotating member, being opposite to each other with about the same size. This in contrast to the structure described in the French patent specification 1,506,445, wherein one of said members is provided with a ring-shaped duct, such that the opening in the other member can be placed in different positions, wherein still a fluidium connecting remains. If a larger number of openings is used such a structure is not desired.
According to a preferred embodiment of the invention the rotating member executes, in view of its large mass, a continuous rotating movement. This can simply be realised with an electromotor or servomotor. The indexing member can be moved along during the movement by the rotating member, but is also possible to use another movement to that end. The fro movement of the auxiliary member is realised according to a preferred embodiment of the invention by an electromotor, being controlled by the controll as described above. Sensors are provided taking care that it is guaranteed that after the return movement the several openings of the auxiliary member and rotating member are exactly aligned above each other. It is possible to determine the position during each return movement with reference to the sensors. The sensors can generate a number of pulses for each motor revolution. These pulses are counted and control both motors both with regard to speed and position. Sensor as used above and the following description can comprise each device being known in the prior art.
According to the invention the auxiliary member, i.e. the xe2x80x98stationaryxe2x80x99 valve plate, realizes a rotation over a restricted angle. Because of that this valve plate realises an indexing movement. This structure can be realized relatively simple and space saving.
A further simplification can be obtained if the valve plate or auxiliary member is provided near the lower side of the columns. Because of that the structure can be realised in a compact way and is simply accessible for service purposes. This is particularly true if higher apparatus are used having a height of e.g. 2-7,5 meters.
With the auxiliary member, stationary valve plate respectively all movements being of importance can be realised. I.e. the stationary valve plate or the auxiliary member follows the rotation of the rotating valve plate or the rotating member over a determined angle and subsequently indexes back with the same angle to effect that the first openings of the rotating members during the first part of this movement are opposite to the first openings of the auxiliary member and to realise after indexing movement that the first openings of the rotating member are opposite to the second openings of the auxiliary member.
The stationary valve plate will be placed in communication with the environment in particular with the aid of flexible hoses, with the result that the limited rotation is permissible.
Controlling the various movements in accordance with the present invention can be considerably simplified with respect to that which is known in the prior art. There are considerably fewer synchronization problems. In the prior art, it is necessary to take special measures in order to avoid problems if the signal for the return movement is not transmitted, or is transmitted too quickly. In the present structure, simple means are sufficient to control the various movements with respect to one another.
To control the above features, sensor means may be present on both the support frame and the auxiliary member. Naturally, locking means or other structures may also be present in order to effect coupling between the auxiliary member and the support frame or the rotating member. However, this will not be necessary for most applications, and the various openings can be brought to lie precisely opposite one another by controlling the drive motor of either the auxiliary member or of the rotating member, or of both. Any inaccuracy could still be eliminated by designing the openings partially in the form of slots.
The above-described limited angle through which the auxiliary member moves with respect to the environment is determined by the number of columns. This angle can be smaller for a larger number of columns.
According to a preferred embodiment of the invention between the auxiliary member and the rotating member a teflon ring is provided. This functions as bearing ring. The friction reducing properties of Teflon are very good as well as its sealing properties. However, it has been found that the speed of the object being the other side of the bearing, i.e. the part sliding over the Teflon should not be too large because otherwise an unacceptable damage of the Teflon ring occurs. If the speed of an energized electromagnet would be used, as known e.g. from the French patent specification 1,506,445, such a damage would occur. By using for example a slower rotating electromotor such damage is avoided.